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Solve for x: 4(3x+7)=7

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sam-mccomb | Student, Grade 9 | eNotes Newbie

Posted June 6, 2009 at 8:00 AM via web

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Solve for x:

4(3x+7)=7

Tagged with algebra, math, solving for x

12 Answers | Add Yours

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buffy-the-vampire-slayer | Student , Undergraduate | eNotes Newbie

Posted June 6, 2009 at 8:48 AM (Answer #1)

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im not sure how your teacher asked you to solve the equations, but theres simple steps to follow to figure out for x;

  1. you want to get rid of the brackets, to do this multiply the numbers in brackets by 4
  2. rewrite the question, it should now be 12x + 28 =7
  3. now you want to isolate x, to do this subtract 28 from both sides of the equation
  4. rewrite the equation once again, it should now be 12x = -21
  5. now divide both sides of the equation by 12
  6. rewrite the equation one more time and you have your answer. x= -1.75
  7. dont forget to check your answer! :)
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kjcdb8er | Teacher | (Level 1) Associate Educator

Posted June 6, 2009 at 8:48 AM (Answer #2)

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4(3x+7)=7

(3x+7)=7/4                    divide both sides by 4

3x = 7/4 - 7              subtract 7 from both sides

x = (7/4 - 7)/3         divide both sides by 3

x = 7/12 -7/3           expand the parenthesis

x = 7/12 - 28/12       find common denominator (* by 4/4)

x = -21/12               subtract

x = -7/4 simplify

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neela | High School Teacher | Valedictorian

Posted June 6, 2009 at 11:26 AM (Answer #3)

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4(3x+7)=7.

To solve for x, multiply by 4 to each of the terms inside the bracket in the left side:4*3x=12x. 4*-7=-28. The right side is retained as it is:

12x+28=7.

Subtract 28 from  both sides to retain the unknown term 12x on the left and the known term or the numbers on the right:

12x+28-28=7-28.

Now 28-28 on the left cancel out.On the right 7-28= -21:

12x=-21.

Divide both sides by 12.  On the left 12x/12 becomes x.On the right -21/12, which is reduced to -7/4 in the lowest equivalent fraction form.

Therefore, x=-7/4  .

Convert 7/4 in decimal form and attach the minus line at last.

7/4=1+3/4 =1.75.

Therefore,x=-1.75 is our solution.

 

Tally:

Put the solution, x=-1.75 in the original equation and see whether the equation is satisfied, in the sense the value on the left becomes equal to the right.

Left side :4*[3(-1.75)+7]=4*3(-1.75)+4*7=4*-5.25+28=-21+28=7.

Right side:7

Both sides are equal in value after putting x=-1.75. So the solution is verified.

 

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Jyotsana | Student , Grade 10 | eNoter

Posted February 9, 2014 at 1:11 AM (Answer #10)

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4(3x+7)=7

12x+28=7

12x+28-28=7-28

12x=-21

12x/12=-21/12

x=-1.75

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fahad-alfahad | eNotes Newbie

Posted June 6, 2009 at 1:01 PM (Answer #4)

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4(3x+7)=7   ======>multiply 4 by 3x , 7

12x + 28 = 7     ========> add -28 both side

12x + 28 -28 = 7-28

12x = -21         =======> divid both side by 12

x = -21/12 = 1.75


 

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sbinkowski | Middle School Teacher | (Level 1) Adjunct Educator

Posted June 14, 2009 at 6:01 AM (Answer #5)

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4(3x + 7) = 7

1) You can't do anything until you get rid of the parentheses. Use distributive property to get rid of those.

12x + 28 = 7

2) Now do the order of operations backwards. The first thing (going backwards) is addition/subtraction. What do you have in your problem? You have addition. The opposite of addition is subtraction.

12x + 28 = 7

-28      -28

12x          = -21

3. Now you have 12x = -21. What operation is being used in the equation? Multiplication is. The opposite of multiplication is division. Now divide both sides by 12.

12x = -21

x = -1.75

 

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fcooper15 | Student , Grade 10 | eNotes Newbie

Posted February 18, 2010 at 11:49 AM (Answer #6)

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4(3x+7)=7

4-3=1 1x7=7

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laurto | Student , Grade 10 | eNoter

Posted December 8, 2013 at 1:32 AM (Answer #8)

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4(3x+7)=7

you have to get rid of the parenthesis

distribute the 4 within the parentheis

12x+28=7

subtract 28 from both sides

12x+28=7

     -28    -28

12x=-21

divide by 12

12x=-21

/12    /12

x=-1.75

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Yojana_Thapa | Student , Grade 10 | eNoter

Posted February 7, 2014 at 11:12 PM (Answer #9)

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4(3x+7)=7

* distribute the 4

  • (4 * 3x)= 12x
  • (4 * 7) = 28

12x + 28 = 7

  • subtract 28 in both sides
  • +28 -28 = 0
  • 7 - 28 = -21

12x = -21

  • Divide 12 to both sides to get the x alone
  • (12x / 12 ) = x
  • (-21/12) = -1.75

x = -1.75

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nicole8923 | Student , Grade 10 | eNoter

Posted February 26, 2014 at 7:43 PM (Answer #11)

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4(3x+7)=7

12x+28=7

12x+28-28=7-28

12x=-21

12x/12=-21/12

x=-1.75

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Wiggin42 | Student , Grade 12 | eNoter

Posted March 23, 2014 at 4:00 PM (Answer #12)

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4(3x+7)=7

Divide both sides by 4

3x + 7 = 7/4

subtract 7

3x = (7/4) - 7

divide by 3

((7/4) - 7)/3

= -1.75

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atyourservice | Student , Grade 10 | eNoter

Posted April 16, 2014 at 3:37 AM (Answer #13)

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4(3x+7)=7

multiply the numbers in the parentheses (3x + 7) by the number on the outside of the parenthesis (4) 
 
`3x xx 4= 12x `
 
 
`4 xx 7 = 28 `
 
 
`12x + 28 = 7 `
 
minus 28 to combine like terms and get x alone
 
12x=-21
 
divide by 12 to get x alone
 
 
`(12x) / 12 = -21 / 12 `
 
x = -1.75

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